1. Field of the Invention
The present invention relates to a processing apparatus for subjecting a workpiece, such as a semiconductor wafer, to a film forming process, and a method of manufacturing the same.
2. Description of the Related Art
Generally, when fabricating a semiconductor integrated circuit, a thin film of a metal or a metal compound, such as W (tungsten), WSi (tungsten silicide), Ti (titanium) TiN (titanium nitride) or TiSi (titanium silicide), is deposited on a semiconductor wafer, i.e., workpiece, to form a wiring pattern on a surface of the semiconductor wafer or to fill up recesses between wiring lines.
The metal thin film of this kind is formed by one of three methods, namely, a SiH2Cl2 (dichlorosilane) reduction method, a SiH4 (silane) reduction method and a H2 (hydrogen) reduction method. The SiH2Cl2 reduction method uses, for example, SiH2Cl2, as a reducing gas and deposits a W film or a WSi film in an environment of a high temperature on the order of 600xc2x0 C. to form a wiring pattern. The SiH4 reduction method uses, for example, SiH4 gas as a reducing gas and deposits a W film or a WSi film in an environment of a high temperature in the range of 350 to 500xc2x0 C. lower than that used by the SiH2Cl2 reduction method to form a wiring pattern. The H2 reduction method uses, for example, H2 gas as a reducing gas and deposits a W film in an environment of a temperature in the range of 350 to 450xc2x0 C. to fill up recesses formed on the surface of a wafer, such as recesses between wiring lines.
All of those methods uses WF6 (tungsten hexafluoride). Referring to FIG. 8 showing a general film forming apparatus for forming such a metal thin film, a thin susceptor 4 formed of a carbonaceous material or an aluminum compound is disposed in a processing vessel 2 formed of aluminum or the like in a cylindrical shape. A transparent quartz plate 6 is disposed under the susceptor 4, and heating devices 8, such as halogen lamps, are disposed under the quartz plate 6. A semiconductor wafer W is supported on the susceptor 4. A vertically movable annular clamping ring 10 is pressed against the peripheral part of the wafer to hold the wafer W on the susceptor 4. A shower head 12 of aluminum is disposed opposite to the susceptor 4. A plurality of gas supply holes 13 are formed in the bottom wall of the shower head 12 in a substantially uniform distribution. Generally, the inner surfaces of the processing vessel 2 and the shower head 12, which are made of aluminum, exposed to the reaction chamber is finished by an anodic aluminum oxide film forming process (process for forming Alumite(copyright)).
Heat rays emitted by the heating devices 8 travel through the transparent quartz plate 6, heats the susceptor 4 to heat the semiconductor wafer W supported on the susceptor 4 indirectly and to maintain the semiconductor wafer W at a predetermined temperature. Meanwhile, process gases including WF6 gas and H2 gas are supplied uniformly over the surface of the wafer W through the gas supply holes 13 of the shower head 12 disposed above the susceptor 4 to form a metal film, such as a W film, on the surface of the wafer W.
When processing a semiconductor wafer by various processes in the processing vessel, generation of minute particles that causes yield reduction must: be suppressed to a minimum. For example, in a film forming process, unnecessary films are deposited inevitably on the inner surfaces of the processing vessel 2 and the shower head 12 when depositing a film on a desired surface of the wafer. The thickness of such unnecessary films increases with the number of processed wafers and, when the thickness exceeds a certain level, the unnecessary films come off the surfaces to produce particles.
Generally, the unnecessary films must be removed by wet cleaning, or dry cleaning using ClF3 gas or the like after a predetermined number of wafers in the range of 1000 to 3000 wafers have been processed. It is desirable from the view point of processing wafers at a high throughput to carry out such a cleaning operation at the longest possible intervals. In the present state of art, however, the interval between the cleaning operations, although dependent on the type of the film, corresponds to a period in which 1000 to 3000 wafers are processed at the longest.
When forming a W film, F contained in WF6 gas, i.e., process gas, attacks a base film, such as a TiN film, formed on a wafer and causes TiF compound or the like to scatter, the TiF compounds reacts with moisture and W to deposit a blue W/Ti/F/O composite compound on the respective inner surfaces of the shower head 12 and the processing vessel 2. Such a W/Ti/F/O composite compound acts as nuclei and promotes the deposition of unnecessary W films, which shortens the intervals of the cleaning operations.
The present invention has been made to solve the foregoing problems effectively and it is therefore an object of the present invention to provide a processing apparatus including metallic components including a processing vessel and having surfaces finished by a special process to make difficult the deposition of unnecessary films on the surfaces and the separation of deposited films from the surfaces in order that the cleaning intervals can be extended, and capable of suppressing production of particles, and to provide a method of manufacturing such a processing apparatus.
Various cleaning methods have been proposed to improve throughput. The inventors of the present invention turned their attention to surfaces on which unnecessary films are deposited, found conditions that makes the deposition of film difficult and have made the present invention.
According to a first aspect of the present invention, a processing apparatus comprises: a processing vessel capable of being evacuated; a susceptor disposed inside the processing vessel to support a workpiece thereon; a shower head disposed in an upper region within the processing chamber to supply process gases toward the workpiece supported on the susceptor for processing the workpiece for a predetermined process; and aluminum members exposed to an interior of the processing vessel, wherein the aluminum members have surfaces processed by an organic mechanical chemical polishing process, a blasting process and an anodic aluminum oxide film forming process in that order.
According to a second aspect of the present invention, a method of manufacturing a processing apparatus comprising a processing vessel capable of being evacuated; a susceptor disposed inside the processing vessel to support a workpiece thereon; a shower head disposed in an upper region within the processing chamber to supply a process gas toward the workpiece supported on the susceptor for processing the workpiece for a predetermined process; and metal members of aluminum exposed to the interior of the processing vessel, comprises a step of subjecting a surface of at least one of the metal members to an organic mechanical chemical polishing process, a blasting process and an aluminum oxide film forming process in that order, and a step of applying the metal members thus processed by those processes in the processing vessel.
When the surfaces of the metal members of aluminum of the processing apparatus are thus processed beforehand, it is difficult for unnecessary films to adhere to the surfaces of the metal members exposed to a processing chamber defined by the processing vessel and films deposited on the same surfaces hardly come off the surfaces. Consequently, the intervals between the cleaning operations can be extended to improve throughput and to suppress production of particles.